Ultrasound mapping of soft tissue vascular anatomy proximal to the larynx: a prospective cohort study
Article information
Abstract
Background
Bleeding incidents during percutaneous dilatational tracheostomy are concerning, and most cases occur in patients with unrecognized and unanticipated anatomical variations in the vascular anatomy. However, the extent of this variation remains unclear. To address this knowledge gap, our study aimed to comprehensively map laryngeal vascular anatomy in a cohort of adult patients.
Methods
Ultrasound assessments of the soft tissue in the neck were performed, spanning from the thyroid cartilage to the third tracheal ring and extending 2 cm laterally on both sidesperformed. We subdivided this area into 12 zones comprising four medial and eight lateral sections. A pre-planned form was used to document the presence of arteries or veins in each zone. The results are reported as odds ratios, 95% CIs, and corresponding P values.
Results
Five-hundred patients were enrolled from August 14, 2023, to November 13, 2023, at the University Hospital of Padua. Arteries and veins were identified in all investigated zones (varying from a minimum of 1.0%–46.4%). The presence of invessels progressively increased from the cricothyroid membrane to the third tracheal ring and from the midline to the paramedian laryngeal area.
Conclusions
Given the prevalence of arteries and veins, particularly in areas where tracheostomies are commonly performed, we strongly advocate for routine ultrasound assessments before such procedures are performed.
Introduction
Up to 24% of patients requiring invasive mechanical ventilation may require tracheostomy [1]. While both surgical and percutaneous dilatational tracheostomy (PDT) have advantages and disadvantages, a meta-analysis including 14 randomized controlled trials and 973 patients showed that PDT is associated with a lower incidence of infection than surgical tracheostomy, despite a higher incidence of technical difficulties [2]. However, bleeding during or immediately after PDT is worrisome, and the most serious bleeding episodes occur in patients with unrecognized and unanticipated anatomical variations in vascular anatomy [3]. Therefore, performing ultrasound (US) assessments before PDT is recommended to reduce the incidence of complications during the maneuver [4]. Initial results from US assessments performed before PDT are promising [5]. However, whether US assessments should be performed as routine practice has not been established [4], as the variability of vascularization in the general population that could undergo this procedure is not known.
In order to investigate this variability, this study aimed to map the vascular anatomy of the soft tissue in front of the larynx in a cohort of adult patients eligible for elective surgery. This study aimed to create a valuable reference tool for clinicians performing percutaneous tracheostomies. Our secondary aims were to establish the odds ratio (OR) for the risk of vessel puncture in different anatomical zone and to determine the OR associated with the potential risk of vessel puncture in individuated anatomical zones.
Materials and Methods
This prospective observational study was conducted in the operating room of the Sant’Antonio University Hospital of Padua. The study protocol, which was designed in accordance with the Helsinki Declaration of 1975 (revised 2013) and its later amendments, was approved by the Ethics Committee for Clinical Research of the University Hospital of Padua (AOP3019/2023) and prospectively registered at Clinicaltrials.gov (NCT06002178). Written informed consent was obtained from all the participants. The inclusion criteria were patients aged > 18 years with a planned US assessment of the neck (e.g., orthopedic or neck surgeries and central venous catheterization), and the exclusion criteria were previous tracheostomy and lack of consent. The following demographic and clinical data were obtained directly from the patient: sex, age, weight, height, and history of previous neck surgery or radiotherapy.
As shown in Fig. 1, the anterior region of the neck was divided into 12 zones, including four medial areas and eight lateral areas. The four medial areas were divided into the thyroid cartilage and cricothyroid membrane (area 2), lower edge of the cricothyroid membrane to the lower edge of the first tracheal ring (area 5), lower edge of the first tracheal ring to the lower edge of the second tracheal ring (area 8), and lower edge of the second tracheal ring to the lower edge of the third tracheal ring (area 11). The eight lateral areas were divided into 2-cm wide lateral quadrants on both the right and left sides of the above-mentioned medial areas (areas 1, 4, 7, and 10 on the left and areas 3, 6, 9, and 12 on the right).
Graphical representation of the individuated zones used in the study.
To identify the vascular structures within each quadrant, ultrasound Doppler examinations were performed with a linear 5–12 MHz probe on both the longitudinal and transverse axes. Arteries were identified as pulsatile anechoic structures, while veins were identified as anechoic non-pulsatile structures.; For both arteries and veins, color Doppler was performed to confirm the first impression. Two experts in vascular ultrasound (MI and ADC) performed all the examinations. The presence of veins (yes/no) or arteries (yes/no) and their sizes in each zone were reported on a pre-planned form. To avoid bias, the carotid arteries and jugular veins were excluded whenever they were identified in the lateral quadrants.
Considering that different patient positions can affect the size of vessels and impede vein identification [6], all patients were evaluated in the supine position. Moreover, to simulate the intrathoracic pressure increase that occurs during positive-pressure mechanical ventilation, patients were asked to perform the Valsalva maneuver during the US exam.
Statistical analysis
Given the observational nature of the study and the lack of previous studies, a formal sample size calculation was not performed. Instead, we enrolled as many patients as possible over a one-year span to a maximum of 500 patients, as approved by the Institutional Review Board. The Shapiro-Wilk test was used to assess the variable distribution normality. Normally distributed continuous variables are described as means ± SD, while non-normally distributed continuous variables are reported as medians (Q1, Q3). Categorical variables are described as absolute numbers (percentages). The results were reported as ORs, 95% CIs, and P values. Statistical significance was set at P < 0.05. All statistical analyses were performed using R version 4.0.2 (The R Foundation for Statistical Computing).
Results
A total of 500 patients were enrolled between August 14, 2023, and November 13, 2023 (Fig. 2). The demographic patient characteristics are shown in Table 1. UUS assessments were successfully completed for each patient, and the results for each zone are reported in Table 2. The lowest proportion of vessels was found in zone 2 (arteries 1.6%, veins 1.0% of the total vessels identified), whereas the highest proportion was in zone 9 (arteries 43.2%, veins 46.4% of the total vessels identified).
Study flowchart.
Demographic Characteristics of Enrolled Patients
Detailed Results for Each Zone Assessed in the Study
We stratified the risk of vessel retrieval for each tracheal ring (Table 3) and between the medial and lateral zones. A lateral puncture during PDT was associated with a higher risk of venous puncture (449 patients [90%]) than a central puncture (133 patients [27%]), with an OR of 24.13 (95% CI [17.12, 34.58], P < 0.001).
Statistical Analysis for the Risk of Vessel Retrieval for Each Tracheal Ring
In addition, a lateral approach was associated with a higher risk of arterial puncture (434 patients [87%]) than a central puncture (141 patients [28%]), with an OR of 16.65 (95% CI [12.11, 23.17], P < 0.001).
Discussion
The main finding of our study was that blood vessels wereare found in all zones surrounding the larynx. Furthermore, the distribution of these vessels is not uniform, but progressively increases from the cricothyroid membrane to the third tracheal ring, and from the midline to the paramedian laryngeal areas.
In our study, we demonstrated that although the risk of puncture during PDT in certain areas may appear to be low, all the regions studied carry a risk of vascular puncture. Bleeding during or immediately after PDT is rare, though not exceptional, thatand accounts for 10% of all PDT-associated complications [7].
A 2012 national survey on catastrophic complications during tracheostomy found that, while bronchoscopy guidance was commonly used (46.5%) [8], US guidance before or after the procedure was not reported [8]. This indicates that the use of US in PDT has not become widespread. Our findings provide support for including US examination ais an assessment tool before PDT.
PDT is typically performed between the second and third tracheal rings because a higher-level tracheostomy is associated with a higher risk of tracheal stenosis and more difficult surgical correction in the subglottic area [9]. However, in emergencies or for patients with unique anatomical features that make conventional locations impractical, PDTs have been performed between the first and second tracheal rings [10]. One mechanism of tracheal stenosis after PDT is tracheal ischemia caused by excessive pressure on the tracheal wall [9]. Based on our results, we hypothesized that reduced vessel representation and blood perfusion in the upper laryngeal region may contribute to a higher incidence of subglottic stenosis. However, further studies employing other imaging techniques such as angiography are necessary to verify this hypothesis.
Our study has some limitations. First, the study was performed at a single center; therefore, our population is not representative of the overall population. Second, two subgroups of patients of particular interest for analysis (history of neck radiotherapy and obese patients) were underrepresented. In the future, studies focusing on these particular subgroups are necessary to verify possible discrepancies with our results.
In conclusion, we found that the cervical region surrounding the larynx is highly vascularized, with a progressive increase in the number of vessels he number from the cricothyroid membrane to the third tracheal ring and from the midline to the paramedian laryngeal areas. Performing US assessments before PDT is strongly recommended.
Acknowledgements
We would like to thank Dr. Sebastiano Negro for creating the illustrations included in this research article.
Notes
Funding
None.
Conflicts of Interest
No potential conflict of interest relevant to this article was reported.
Data Availability
The datasets and analyzed during the current study are available from the corresponding author on reasonable request.
Author Contributions
Alessandro De Cassai (Conceptualization; Data curation; Formal analysis; Investigation; Methodology; Validation; Writing – original draft; Writing – review & editing)
Margherita Iuzzolino (Conceptualization; Data curation; Investigation; Writing – original draft; Writing – review & editing)
Silvia De Pinto (Writing – original draft; Writing – review & editing)
Giovanni Zecchino (Writing – original draft; Writing – review & editing)
Tommaso Pettenuzzo (Writing – original draft; Writing – review & editing)
Annalisa Boscolo (Writing – original draft; Writing – review & editing)
Eugenio Biamonte (Writing – original draft; Writing – review & editing)
Paolo Navalesi (Supervision; Writing – original draft; Writing – review & editing)
Marina Munari (Supervision; Writing – original draft; Writing – review & editing)